The effect of incorporation of different concentrations of ethanol as a solvent on the microshear bond strength of a solvent-free dentin bonding agent

Different studies have demonstrated that resin penetration into collagen fibers is influenced and promoted by the presence of a solvent in the bonding agents, but in order to create a reliable bond, it should be removed before curing. This study investigates the effect of adding ethanol as a solvent on the microshear bond strength of a solvent-free dentin bonding agent. After removing the occlusal enamel of 20 caries-free human third molars, midcoronal dentin slices, each about 2 mm thick were prepared then polished by silicon paper. The superficial dentin surfaces were randomly distributed into four groups and treated with James-2 containing different concentrations of ethanol (0, 5, 10, and 20 wt%) in two layers and then light-cured. The micro shear bond strength (µSBS) was tested using a universal testing machine. The data were finally subjected to one-way ANOVA followed by Tukey's post-hoc test. James-2 containing 5 wt% ethanol provided the highest micro-shear bond strength (32.1 ± 6.69 MPa). There were no statistical differences in µSBS values between other groups (25 ± 5.8 MPa, 24.8 ± 4.93 MPa and 21.8 ± 4.51 MPa, respectively). Adding ethanol as a solvent resulted in increased micro shear bond strength to dentin. At higher solvent concentrations no significant change was observed indicating that the solvents may not have been completely removed leading to poor polymerization and porosity reflected as lower bond strengths.